We propose to develop mucosal vaccines to HIV-1 designed to induce immune responses to block the initial steps of sexual transmission of HIV 1, that is infection through the genital mucosa and dissemination of virus to the draining lymph nodes. The vaccine will be based on El-deleted adenoviral recombinants. Such vaccines can be developed for the envelope protein for induction of neutralizing antibody responses or for more conserved internal proteins such as the capsid protein (Gag) for induction of cross-reactive cytolytic T cell responses. In this proposal, we will focus on CD8+ T cell-mediated immune responses induced by recombinants expressing the Gag (with or without polymerase [Pol]) in an experimental model utilizing female inbred mice. In the first aim we will test adenoviral recombinants of the human strain 5 carrying wild type or codon 'optimized' forms of gag. Recombinants will be analyzed in mice for induction of CD8+T cell responses to Gag in spleens, lymph nodes draining the genital tract and vaginal tissue after systemic or intranasal immunization. Vaccine efficacy will be assessed with a surrogate model testing for inhibition of replication of a vaccinia virus recombinant expressing Gag in mouse ovaries following intraperitoneal challenge. In the second aim, we will explore adenoviral recombinants to Gag based on a simian strain to circumvent interference with pre-existing immunity to human strains in a clinical setting. In the third aim, we will test a prime-boost regimen using DNA vaccines, expressing Gag for systemic priming combined with the adenoviral recombinants for systemic or intranasal booster immunization.